To attach a Vacu-Stack to a masonry flue, begin by sealing the Vacu-Stack Masonry Adaptor to the top of the flue tile with silicone sealant.

Then turn the wing nut device that extends the ends of the threaded rod at the sides of this adaptor until the ends of the rod are wedged at the corners of the flue. The Vacu-stack itself then simply fits into the round portion of the adaptor.